#include <stdio.h>
 int main()
 {
 	int score;
	while(scanf("%d",&score)!=EOF)
	{
	
	if(score > 100 || score < 0)
	{
		printf("Score is error!\n");
		continue;
	}
	score = score / 10;
	switch(score)
	{
	case 10:
	case 9:
		printf("A\n");
		break;
	case 8:
		printf("B\n");
		break;
	case 7:
		printf("C\n");
		break;
	case 6:
		printf("D\n");
		break;
	default:
		printf("E\n");
		break;
	}
	}
	return 0;
}
